Adjacent Field Alignment

ABSTRACT

Methods for imprinting on abutted fields of a substrate are described. Generally, a first field of a substrate may be imprinted using an imprint lithography template. The template may then be placed such that a portion of the template overlaps the first field of the substrate while imprinting a second field of the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Application No. 61/231,182 filed Aug. 4, 2009, which is hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The United States government has a paid-up license in this invention and the right in limited circumstance to require the patent owner to license others on reasonable terms as provided by the terms of 70NANB4H3012 awarded by National Institute of Standards (NIST) ATP Award.

BACKGROUND INFORMATION

Nano-fabrication includes the fabrication of very small structures that have features on the order of 100 nanometers or smaller. One application in which nano-fabrication has had a sizeable impact is in the processing of integrated circuits. The semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, therefore nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing continued reduction of the minimum feature dimensions of the structures formed. Other areas of development in which nano-fabrication has been employed include biotechnology, optical technology, mechanical systems, and the like.

An exemplary nano-fabrication technique in use today is commonly referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as U.S. Patent Publication No. 2004/0065976, U.S. Patent Publication No. 2004/0065252, and U.S. Pat. No. 6,936,194, all of which are hereby incorporated by reference herein.

An imprint lithography technique disclosed in each of the aforementioned U.S. patent publications and patent includes formation of a relief pattern in a formable (polymerizable) layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be coupled to a motion stage to obtain a desired positioning to facilitate the patterning process. The patterning process uses a template spaced apart from the substrate and a formable liquid applied between the template and the substrate. The formable liquid is solidified to form a rigid layer that has a pattern conforming to a shape of the surface of the template that contacts the formable liquid. After solidification, the template is separated from the rigid layer such that the template and the substrate are spaced apart. The substrate and the solidified layer are then subjected to additional processes to transfer a relief image into the substrate that corresponds to the pattern in the solidified layer.

BRIEF DESCRIPTION OF DRAWINGS

So that the present invention may be understood in more detail, a description of embodiments of the invention is provided with reference to the embodiments illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the invention, and are therefore not to be considered limiting of the scope.

FIG. 1 illustrates a simplified side view of a lithographic system in accordance with an embodiment of the present invention.

FIG. 2 illustrates a simplified side view of the substrate shown in FIG. 1 having a patterned layer positioned thereon.

FIG. 3 illustrates a simplified side view of a template and a substrate having extrusions formed thereon.

FIG. 4 illustrates a flow chart of a method for imprinting multiple fields to minimize and/or prevent extrusions.

FIG. 5 illustrates a flow chart of a method for retracting polymerizable material from at least one edge of an imprinting area to minimize and/or prevent extrusions.

FIG. 6 illustrates a top down view of a substrate having retracted polymerizable material retracted from edges of an imprinting area.

FIG. 7 illustrates one embodiment of a stepping pattern.

FIG. 8 illustrates a simplified side view of a template overlapping at least a portion of a patterned field during imprinting.

FIG. 9 illustrates a flow chart of a method for imprinting a field using overlap imprinting.

DETAILED DESCRIPTION

Referring to the figures, and particularly to FIG. 1, illustrated therein is a lithographic system 10 used to form a relief pattern on substrate 12. Substrate 12 may be coupled to substrate chuck 14. As illustrated, substrate chuck 14 is a vacuum chuck. Substrate chuck 14, however, may be any chuck including, but not limited to, vacuum, pin-type, groove-type, electrostatic, electromagnetic, and/or the like. Exemplary chucks are described in U.S. Pat. No. 6,873,087, which is hereby incorporated by reference herein.

Substrate 12 and substrate chuck 14 may be further supported by stage 16. Stage 16 may provide motion along the x, y, and z axes. Stage 16, substrate 12, and substrate chuck 14 may also be positioned on a base (not shown).

Spaced-apart from substrate 12 is template 18. Template 18 may include mesa 20 extending therefrom towards substrate 12, mesa 20 having a patterning surface 22 thereon. Further, mesa 20 may be referred to as mold 20. Alternatively, template 18 may be formed without mesa 20.

Template 18 and/or mold 20 may be formed from such materials including, but not limited to, fused-silica, quartz, silicon, organic polymers, siloxane polymers, borosilicate glass, fluorocarbon polymers, metal, hardened sapphire, and/or the like. As illustrated, patterning surface 22 comprises features defined by a plurality of spaced-apart recesses 24 and/or protrusions 26, though embodiments of the present invention are not limited to such configurations. Patterning surface 22 may define any original pattern that forms the basis of a pattern to be formed on substrate 12.

Template 18 may be coupled to chuck 28. Chuck 28 may be configured as, but not limited to, vacuum, pin-type, groove-type, electrostatic, electromagnetic, and/or other similar chuck types. Exemplary chucks are further described in U.S. Pat. No. 6,873,087, which is hereby incorporated by reference herein. Further, chuck 28 may be coupled to imprint head 30 such that chuck 28 and/or imprint head 30 may be configured to facilitate movement of template 18.

System 10 may further comprise fluid dispense system 32. Fluid dispense system 32 may be used to deposit polymerizable material 34 on substrate 12. Polymerizable material 34 may be positioned upon substrate 12 using techniques such as drop dispense, spin-coating, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), thin film deposition, thick film deposition, and/or the like. Polymerizable material 34 may be disposed upon substrate 12 before and/or after a desired volume is defined between mold 20 and substrate 12 depending on design considerations. Polymerizable material 34 may comprise a monomer mixture as described in U.S. Pat. No. 7,157,036 and U.S. Patent Publication No. 2005/0187339, both of which are hereby incorporated by reference herein.

Referring to FIGS. 1 and 2, system 10 may further comprise energy source 38 coupled to direct energy 40 along path 42. Imprint head 30 and stage may be configured to position template 18 and substrate 12 in superimposition with path 42. System 10 may be regulated by processor 54 in communication with stage 16, imprint head 30, fluid dispense system 32, and/or source 38, and may operate on a computer readable program stored in memory 56.

Either imprint head 30, stage 16, or both vary a distance between mold 20 and substrate 12 to define a desired volume therebetween that is filled by polymerizable material 34. For example, imprint head 30 may apply a force to template 18 such that mold 20 contacts polymerizable material 34. After the desired volume is filled with polymerizable material 34, source 38 produces energy 40, e.g., ultraviolet radiation, causing polymerizable material 34 to solidify and/or cross-link conforming to a shape of surface 44 of substrate 12 and patterning surface 22, defining patterned layer 46 on substrate 12. Patterned layer 46 may comprise a residual layer 48 and a plurality of features shown as protrusions 50 and recessions 52, with protrusions 50 having a thickness t₁ and residual layer having a thickness t₂.

The above-mentioned system and process may be further employed in imprint lithography processes and systems referred to in U.S. Pat. No. 6,932,934, U.S. Patent Publication No. 2004/0124566, U.S. Patent Publication No. 2004/0188381, and U.S. Patent Publication No. 2004/0211754, each of which is hereby incorporated by reference herein.

Referring to FIG. 3, during imprinting, drops of polymerizable material 34 fill the volume between features 24 and 26 of template 18 and the edge of mesa 20 within a desired imprint area on substrate 12. Polymerizable material 34, however, may flow out of this desired imprint area on substrate 12 forming extrusions 60 a on substrate 12 as illustrated in FIG. 3. For example, extrusions 60 a on substrate 12 may be formed during imprinting of Field A and/or Field C.

Extrusions 60 b on template 18 also may be formed during imprinting of Field A and/or Field C. Extrusions 60 a and/or 60 b may inhibit formation of imprinting Field B. For example, extrusions 60 a may form an asperity on substrate 12 exceeding the height of thickness t₂, of residual layer 48 a of Field A and/or thickness t_(2c) of residual layer 48 c of Field C. As such, extrusions 60 may inhibit formation of the imprinting field (Field B) by preventing template 18 from attaining a suitable distance from substrate 12.

In the prior art, imprint fields of substrate 12 are separated such that the imprinting area of template 18 does not overlap the previous imprinted field. This process, however, may provide patterned layer 46 having discontinuity in residual layer 48 especially when space between fields is provided to accommodate for extrusions 60 a and/or 60 b. In CMOS processing (e.g., etching, chemical-mechanical polishing (CMP), and the like), generally residual layer 48 has a substantially constant average thickness t₂ without such discontinuity between fields. Additionally, the entire surface of substrate 12 provides valuable real-estate that should be maximized to avoid waste. Separation of imprint fields to avoid overlapping may waste this valuable real-estate.

FIGS. 4-7 describe and illustrate various process methods that may minimize and/or prevent extrusions 60. Further, such methods may provide for imprinting of abutted fields on substrate 12. It should be noted that such techniques may be used singularly or in combination to minimize and/or prevent extrusions 60.

FIG. 4 illustrates a flow chart of a method 100 for imprinting multiple fields to minimize and/or prevent extrusions 60 a and/or 60 b. Generally, minimizing thickness t₂ of residual layer 48 may minimize the total amount of polymerizable material 34 on substrate and thereby minimize occurrence of extrusions 60 a and/or 60 b. In a step 102, a first volume V₁ of polymerizable material 34 may be determined to minimize the thickness t_(2a) of residual layer 48 of a first field (Field A) of a substrate 12 (e.g., less than approximately 25 nm). In a step 104, first volume V₁ of polymerizable material 34 may be deposited on substrate 12 at first field (Field A). In a step 106, template 18 may contact polymerizable material 34. In a step 108, polymerizable material 34 may be solidified. In a step 110, template 18 may be separated from polymerizable material 34 to provide first patterned layer 48 a at first field (Field A). In a step 112, a second volume V₂ of polymerizable material 34 may be determined to minimize the thickness t_(2b) of residual layer 48 b of a second field (Field B) of a substrate 12 (e.g., less than approximately 25 nm). Second field (Field B) may be adjacent and abutting first field (Field A). Second volume V₂ may be substantially similar to first volume V₁. Alternatively, second volume V₂ may be different than first volume V₁. For example, if deposition of material on substrate in first field (Field A) and second field (Field B) is at a substantially similar time, second volume V₂ may be increased to account for evaporation of polymerizable material as first field (Field A) may be imprinted prior to second field (Field B).

In a step 114, second volume V₂ of polymerizable material 34 may be deposited on substrate 12 at second field (Field B). In a step 116, template 18 may contact polymerizable material 34. In a step 118, polymerizable material 34 may be solidified. In a step 120, template 18 may be separated from polymerizable material 34 to form second patterned layer 48 b at second field (Field B). Second patterned layer 48 b at second field (Field B) may have a residual layer 48 b substantially similar to residual layer 48 a of first patterned layer 48 a of at first field (Field A).

FIG. 5 illustrates another method for limiting and/or eliminating extrusions 60 a and/or 60 b. In particular, flow chart 200 illustrates of a method for retracting polymerizable material 34 from at least one edge of the imprinting area to minimize and/or prevent extrusions 60 a and/or 60 b. In a step 202, a drop pattern for dispensing of polymerizable material 34 on a field may be determined. For example, the drop pattern may be determined by correlating features 24 and/or 26 of template 18 with required volume and/or thickness of residual layer 48 a such that drops are spatially correlated to location of features 24 and/or 26 of template 18 and in sufficient quantity to fill volume between template 18 and substrate 12 during imprinting. Exemplary techniques for determination of drop patterns by correlation of features 24 and/or 26 may be found in at least U.S. Ser. No. 11/143,092, U.S. Ser. No. 12/170,229, and U.S. Ser. No. 12/262,669, all of which are hereby incorporated by reference in their entirety.

In a step 204, drop pattern may be adjusted such that drops at edges of drop pattern (e.g., located at edges of patterned layer 48 a and/or at edge of the imprinting area) may be offset towards the center C of the drop pattern (e.g., towards center of Field A). For example, drops may be offset toward the center C of Field A such that during imprinting, features 24 and 26 and the volume between template 18 and substrate 12 may be filled before polymerizable material 34 has an opportunity to flow off mesa 20.

FIG. 6 illustrates one example of offsetting drops toward the center C of Field A by a distance d. Distance d may be a perimeter established about edges 64 of a field. For example, distance d may be a perimeter established about edges 64 of a field at approximately 200 μm. Generally, distance d is substantially similar at all edges 64 of the imprinting field; however, it should be noted that distance d may be different at one or more edges 64 of imprinting field depending on design considerations. For example, distance d may be similar for parallel edges. Further, the magnitude of distance d may be altered based on prior abutting imprinted fields and/or distribution of features 24 and/or 26 of template 18. For example, edge 64 of a field that is abutted next to a prior imprinted field may have a greater distance than another edge 64 of the field. Offsetting may be substantially similar at each edge 64 of the field or such offset distance d may be different at each edge 64 of the field. In one example, the number of drops needed to form an imprint may not be reduced during adjustment of drop pattern; rather drops may be solely offset toward the center of the field.

In a step 206, polymerizable material 34 may be deposited on substrate 12 based on the adjusted drop pattern. In a step 208, distance between template 18 and substrate 12 may be minimized as polymerizable material 34 from drops placed at perimeter of imprinting area according to the adjusted drop pattern reach an edge of mold 20. In a step 210, polymerizable material 34 may be solidified. In a step 212, template 18 may be separated from solidified polymerizable material 34 forming patterned layer 48 a in Field A of substrate 12. In a step 214, each of the above steps may be repeated for Field B of substrate 12. Residual layers 48 of Field B and Field A may have substantially similar thickness t₂.

Referring to FIG. 7, a stepping pattern 400 may be used to optimally equalize the number of times each edge 64 of a field is abutted to a previously imprinted field. Providing stepping pattern 400 may minimize deposition of polymerizable material 34 off mold 20 during imprinting as described and illustrated in FIGS. 1 and 2. Stepping pattern 400 generally arranges imprint order of fields on substrate 12 such that during imprinting each edge 64 of field abuts a prior imprinted field edge 64. Prior imprinted edges 64 are indicated by dark rectangles in FIG. 7. Edges 64 of prior imprinted fields may be used to contain or provide a boundary for polymerizable material 34 thus minimizing deposition of polymerizable material 34 off of mold 20.

FIG. 7 illustrates stepping pattern 400 wherein each field of substrate 12 is depicted as a square designated by an imprint order. In this stepping pattern 400, the first field (reference number 1) is imprinted in the center of substrate 12 with each subsequent field (reference numbers 2, 3, 4, 5 . . . 34) being imprinted in a spiral-like fashion towards the edge 66 of substrate 12. Using the spiral-like imprinting pattern, each edge 64 of a field may abut at least one prior imprinted field (indicated by dark rectangle) with the edge 64 of the field to be imprinted. The edge 64 adjacent to a prior imprinted field is indicated a by dark rectangle. This edge 64 may provide containment of polymerizable material 34 for the field being imprinted. For example, during the imprinting of field 6, one edge 64 of prior imprinted field 1 and one edge 64 of prior imprinted field 4 may provide containment of polymerizable material 34.

Referring to FIGS. 3, 8 and 9, an overlap imprint method 500 may be used to confine polymerizable material 34 between edges of previously imprinted fields, and minimize and/or prevent extrusions 60 a and 60 b. Referring to FIGS. 8 and 9, in a step 502, Field A may be imprinted to form patterned layer 46 a having residual layer 48 a using systems and processes related to FIGS. 1 and 2. Optionally, Field C may be imprinted to form patterned layer 46 c having residual layer 48 c. In a step 504, template 18 may be positioned in superimposition with Field B such that at least a portion 19 a of template 18 is in superimposition with at least a portion of patterned layer 46 a of Field A. Template 18 may include a first side 70 and a second side 72. First side 70 may include features 24 and 26 as described in relation to FIG. 1. Portion 19 a of template 18 overlapping patterned layer 46 a may be substantially planar and positioned adjacent to features 24 and 26. Generally, as features 24 and 26 of template 18 contact polymerizable material 34 during the imprint process (described in detail in relation to FIGS. 1 and 2), portion 19 a is at a slight distance from prior imprinted patterned layer 46 of an adjacent field (e.g., patterned layer 46 a of Field A). The distance is such that features 24 and 26 of template 18 may contact polymerizable material 34 and portion 19 a does not contact prior imprinted patterned layer 46.

Portion 19 a of template 18 may extend (i.e. overlap) over patterned layer 46 a a distance d₂ as illustrated in FIG. 8. Generally, portion 19 a may extend over residual layer 48 a of patterned layer 46 a. Thickness of residual layer 48 a becomes a concern in the overlapping of portion 19 a, as a relatively thick residual layer 48 a may inhibit imprinting of the adjacent field. In one example, thickness of residual layer 48 a is less than 5 μm to provide for imprinting of the adjacent field without inhibiting contact between template 18 and polymerizable material 34 positioned on the adjacent field.

Optionally, portion 19 b of template 18 may extend over another adjacent field (e.g., patterned layer 46 c) simultaneously at a distance d₃. Distance d₂ and d₃ may be substantially similar or different. In a step 506, polymerizable material 34 may be deposited or coated on substrate 12 in the region of Field B. In a step 508, Field B may be imprinted using system and processes of FIGS. 1 and 2.

Referring again to FIG. 3, it should be noted that by minimizing gas flow during the imprinting process, formation of extrusions 60 a and/or 60 b may be minimized and/or prevented. Deposition of polymerizable material 34 on mold and/or template 18 may contribute to formation of extrusions 60. As such, by adjusting gas flow, vapor born polymerizable material 34 may be minimized. By minimizing deposition of polymerizable material 34 on mold 20 (e.g., wall of mold 20), extrusions 60 a and/or 60 b may be minimized and/or prevented. 

1. A method comprising: imprinting, with an imprint lithography template, a first portion of polymerizable material positioned within a first field of a substrate; separating the template from the first portion of polymerizable material forming a first patterned layer; overlapping the template with a portion of the first field and a portion of a second field; imprinting, with the template, a second portion of polymerizable material positioned within the second field of the substrate; and, separating the template from the second portion of polymerizable material forming a second patterned layer.
 2. The method of claim 1, wherein the first patterned layer includes a first residual layer and the second patterned layer includes a second residual layer.
 3. The method of claim 2, wherein thickness of the first residual layer and the second residual layer is substantially similar.
 4. The method of claim 2, wherein volume of the first portion of polymerizable material is determined to minimize thickness of the first residual layer.
 5. The method of claim 4, wherein thickness of the first residual layer is less than approximately 25 nm.
 6. The method of claim 2, further comprising: determining a drop pattern for dispensing of the first portion of polymerizable material on the first field of the substrate; adjusting the drop pattern such that drops of the drop pattern are offset a distance towards a center of the drop pattern, wherein distance establishes a perimeter at edges of the drop pattern removed of drops; and, dispensing polymerizable material on the first field of the substrate using the adjusted drop pattern.
 7. The method of claim 6, wherein the drop pattern for the first portion is determined by correlating features of the template with a required thickness of the first residual layer such that drops of polymerizable material dispensed on the substrate are spatially correlated to locations of features of the template and insufficient quantity to fill a volume between the template and the substrate during imprinting.
 8. The method of claim 6, wherein the distance is substantially similar at all edges of the drop pattern.
 9. The method of claim 6, wherein the distance is different at least one edge of the drop pattern.
 10. The method of claim 6, wherein the distance is greater at an edge of the drop pattern wherein a prior imprinted field is known to be located.
 11. The method of claim 1, further comprising: imprinting a plurality of fields using a stepping pattern to equalize the number of times an edge of a field is abutted to a previously imprinted field.
 12. The method of claim 11, wherein the stepping pattern proceeds in a spiral-like pattern.
 13. The method of claim 11, wherein the abutted field provides containment of polymerizable material for the field being imprinted.
 14. A method, comprising: imprinting a first field using an imprint lithography template to form a first patterned layer having a first residual layer, the imprint lithography template having a first side and a second side, the first side having a plurality of features and at least one substantially planar portion adjacent to the features; positioning the imprint lithography template such that features of the first side are in superimposition with a second field and the planar portion is in superimposition with the first patterned layer; and, imprinting the second field to form a second patterned layer having a second residual layer.
 15. The method of claim 14, wherein thickness of the first residual layer is substantially similar to thickness of the second residual layer.
 16. The method of claim 14, wherein thickness of the first residual layer is less than about 5 μm.
 17. The method of claim 14, wherein a second planar portion of the imprint lithography template is in superimposition with a third patterned layer.
 18. The method of claim 14, wherein the planar portion is in superimposition with the first field during imprinting of the second field and at a distance from the first residual layer.
 19. A method for forming a patterned layer with an imprint lithography template, comprising: positioning the imprint lithography template over polymerizable material deposited on a first field of a substrate; reducing the distance between the template and the substrate such that the template contacts the polymerizable material; solidifying the polymerizable material; separating the template from the polymerizable material forming a first patterned layer; positioning the imprint lithography template over the first patterned layer and polymerizable material deposited on a second field of the substrate; reducing the distance between the template and the substrate such that the template contacts the polymerizable material positioned on the second field; solidifying the polymerizable material; separating the template from the polymerizable material forming a second patterned layer.
 20. The method of claim 19, wherein thickness of residual layers of the first and second patterned layers are substantially similar. 